SPECIAL REPORT: How Energy Efficient Can You Get?

Everybody talks about energy efficiency. In just the past decade—okay, 11 years—a lot has happened. Energy Star has set standards for eight equipment categories, and updates and new categories are always in the works. The federal government has issued minimum standards, the California Energy Commission has set standards and other states have or are contemplating similar ones. Several organizations now offer energy guidelines. Leadership in Energy and Environmental Design (LEED) certification offers points for energy savings. Utilities all over the country are offering rebates for efficient equipment.

But what’s the sum total of what’s possible in current technology? If you tallied everything you could do to cut energy usage—much of which has been covered in FER one topic at a time over the years—how much could you really save in practical terms? The U.S. Department of Energy (DOE) has been working on that question for several categories of buildings for quite a while now, and a couple of years ago it turned its attention to foodservice. Specifically, it narrowed its topic to Quick-Service Restaurants, and the goal was to see whether QSRs could feasibly cut whole-building consumption by half.

PNNL, With FNi, Halton & Seattle Lighting

It turns out QSRs can come close, and because process loads are such a big chunk of total load in foodservice, the findings have significant implications for other foodservice categories as well.

To find out what QSRs can do, the DOE commissioned Pacific Northwest National Laboratory (PNNL), Richland, Wash., to conduct a study to sort it all out. A lot of specialized input would be invaluable, PNNL knew, so it assembled an eight-member author team from multiple companies: Project Manager Bing Liu, Jason Zhang and Rahul Athalye came from PNNL; Don Fisher and David Zabrowski from Fisher-Nickel inc. at Pacific Gas & Electric Co.’s Food Service Technology Center, San Ramon, Calif., joined up; Dr. Andrey Livchak and Derek Schrock from Halton Co., Scottsville, Ky., teamed up; and Michael Lane from Seattle Lighting Design Lab signed on, too. Additionally, several PNNL personnel offered significant support.

In September 2010, PNNL published “Technical Support Document: 50% Energy Savings For Quick-Service Restaurants,” (pnl.gov/main/publications/external/technical_reports/PNNL-19809.pdf) a 145-pager that meticulously sets definitions and procedures, right down to accounting for building air leakage, bathroom exhaust-fan energy, etc., and concludes a “typical” QSR could in fact cut energy consumption by something approaching 50% and, in some cases, could do even better.

Devils & Details

To really get the full picture in all its rich—if wonky—texture, you owe it to yourself to cruise through the report firsthand, download it and take notes. But in the meantime, some basics and highlights:

The DOE was hoping to find ways to hit that 50% energy-reduction target with a key qualifier: simple payback in five years or less. (Yes, less is better, but for lifetime equipment, things can stretch out.) DOE also wanted to hit that 50% level for all eight of the Int’l. Energy Conservation Code climate regions that occur in the U.S. Further, DOE subdivided several of the more sprawling regions into moist, dry and marine, for a total of 16 climate zones as noted in the DOE map shown here. Then one test city was selected in each zone. So 16 test cities were selected. Hit 50% in all of ’em if possible, the DOE said.

Setting The Baseline

As for the standard QSR referenced in the study, based on data from numerous preexisting studies the research team settled on a very prototypical profile: 2,500 sq. ft., a roughly 70’ x 35’ typical rectangular footprint, half front of house and half back, with slab-on-grade floor, wood-framed exterior walls with stucco over and flat roof with insulation entirely above the deck. Construction would “just meet minimal code-compliant requirements of ANSI/ASHRAE/IESNA Standard 90.1-2004, Energy Standard for Buildings Except Low-Rise Residential Buildings, before renewable energy is used,” the study says.

For those components, system configurations and operations that are not regulated by Standard 90.1-2004, PNNL based the model inputs “on common design practices, metering data, and professional judgments.”

Equipment packages can vary a lot based on menu, of course, so the team had to further narrow the baseline definition, settling on a typical hamburger concept. Again with data from other studies in mind, the team determined its cookline. Under the hood were two 3-ft. gas griddles rated at 90kBtu/hr. each, four 15-in. gas fryers at 122kBtu each and a 15-in. dump station. Total Btu came in at 668kBtu. The brand/models were specific, with performance test data already established.

For breakfast hours, a half-size convection oven with known performance data was included in the calculations.

The two hoods were canopy style, each 92-in. x 48-in., each 300 cfm/ft., each 2,300 cfm.

Refrigeration consisted of a 100-sq.-ft. walk-in cooler, an 80-sq.-ft. walk-in freezer and a package of nine pieces of reach-in, undercounter and prep-table refrigerators, freezers and ice machines.

Operations were assumed to be 6 a.m. to midnight Monday through Friday, and from 7 a.m. to midnight Saturday and Sunday, a total of 128 business open hours per week. The extended hours for staff members for preparation and cleaning were one hour before and one hour after the business open hours.

Occupancy, equipment usage (hours/day at idle, light, medium and heavy volume) and other variables all were modeled based on data from previous industry studies.

PNNL used EnergyPlus, the report notes, a state-of-the-art energy-simulation program, to calculate savings of the various tested Energy Efficiency Measures (EEMs).

Good News & Bad

The bad news, if you’re a Gloomy Gus, is that the 50% whole-building goal was not widely feasible. But the very good news was that mid-40% looks entirely reasonable.

“Although the study found that a national-weighted-average energy savings of 45% can be achieved,” the study says, “only the two coldest climates were able to reach the 50% energy-saving target.” So Regions 7 and 8—places like Duluth, Minn., and Fairbanks, Alaska, hit the half. Still, 45% is a worthwhile incentive everywhere else.

The big dough, probably no surprise, is in cooking and refrigeration energy. “Process loads constitute 45% to 65% of whole-building energy consumption in a typical QSR,” the study notes. Testers “achieved significant energy savings in this area with optimized kitchen ventilation systems and innovative food preparation/storage technologies.” Interestingly, the study points out that if process loads are removed from the equation, energy savings “from the building-related components are well beyond the 50% energy saving goal, ranging from 55% in warm climates to 65% in cold climates.”

Saving In The Kitchen

Among the recommended EEMs implemented in the kitchen, the main thing was an upgrade to the highest-rated Energy Star and California-rebate qualified equipment: The two baseline single-sided 3’ griddles (actual width 40”, rated at 90kBtu/hr.) were replaced with two gas/electric double-sided griddles—one a 28” rated at 96kBtu/hr. and the other a 40” unit at 143kBtu/hr. Meanwhile, the four baseline gas fryers were swapped out for three—a 2’ and a pair of 15” high-efficiency units, each rated for 120kBtu/hr.

And likewise, the half-size convection oven was replaced with a high-efficiency oven. The study notes the upgraded oven has “a higher nameplate input rating but has a significantly lower usage factor resulting in a lower overall energy consumption during the day.”

All of the refrigeration pieces got the same upgrade to top-of-class Energy Star pieces where applicable, and where E-Star doesn’t do a rating, the best California rebate-eligible pieces were used.

Savings Everywhere Else

As you can see in the accompanying table of recommended EEMs, issues were addressed in the building envelope and HVAC as well as in kitchen equipment. For many of you who’ve been digging through energy efficiency for years, the lists don’t hold a lot of surprises, at least not piece by piece. But the cumulative effects of combining the various techniques are eye-opening to say the least.

Quite a few of you already have implemented some of the recommendations, obviously. But odds are good that nobody has done all of them. There’s clear indication that virtually everyone can learn something from the study.

ENVELOPE Enhanced building opaque insulation:Exterior walls: R-13 to R-13 plus R-18.8 continuous insulation in various climatesRoofs: R-20 to R-35 in various climatesFloors: up to R-20 vertical insulationHigh-performance window glazing: Double-pane windows with low-emissivity film and high visible transmittance for daylight harvestingCool roofs in climate zones 1 through 3